Patent EP-A-1090839 describes a volumetric metering apparatus for metering a pasty product applicable to the meat industry, comprising an inlet conduit through which the pasty product is supplied, a metering chamber in which the portions of pasty product are metered, and an outlet conduit through which the metered portions are sent to other apparatuses, such as a stuffing machine or the like for example. The inlet conduit, the metering chamber and the outlet conduit are communicated through a valve device which can adopt a first position to allow a flow of pasty product from the inlet conduit to the metering chamber, and a second position to allow a flow of pasty product from the metering chamber to the outlet conduit.
The valve device has a valve body with a cylindrical cavity having a first radial opening connected to the inlet conduit, a second axial opening connected to the metering chamber, and a third tangential opening connected to the outlet conduit. Inside the cavity of the valve body there is rotatably arranged a valve plug having a cylindrical outer surface and a radial and axial passage forming an elbow therethrough. The valve plug is moved by drive means between a first position, in which the first and second openings are mutually communicated through said radial and axial passage of the valve plug and the third opening is shut by said cylindrical outer surface of the valve plug, and a second position in which the first opening is shut by the cylindrical outer surface of the valve plug and the second and third openings are mutually communicated through the radial and axial passage of the valve plug.
A drawback of this valve device included in the volumetric metering apparatus described in the mentioned patent EP-A-1090839 is that the elbow defined by the radial and axial passage through the valve plug is an obstacle which causes a loss of pressure in the flow of pasty product from the inlet conduit to the metering chamber and from the metering chamber to the outlet conduit.